Planetary mass-radius diagram. Vertical regions indicate the minimum mass within 1σ of the planets detected around KOBE-1 (blue for planet b, and green for c). Darker green region shows the 1σ location for KOBE-1 c if we assume it causes the single-TESS transit (solely for illustrative purposes; see more in Sect. 4.2 and Appendix C). Different radius-mass models are shown as identified in the legend to guide the reader on the separated populations (blue lines trace tracks for superEarths and orange lines for sub-Neptunes; Zeng et al. 2019; Aguichine et al. 2021). CMF and WMF refer to the core and water mass fractions, respectively.